In power generation systems for large scale electricity generating applications, the gas turbine is typically used to drive a synchronous generator which provides the electrical power output of the system. As it is of primary importance that the electrical output is not interrupted, especially in transient and emergency conditions that can lead to total or partial blackouts, these power generation systems are typically equipped with emergency power supply systems, which are independent power generation systems, assuring uninterrupted power supply in cases of failure or disruption.
Uninterruptible power supply (UPS) systems are known emergency power supply systems in the state of the art, automatically providing emergency power, without delay or transients, to critical applications in case of an interruption or an unacceptable condition of the main supply provided by the power generation system. Typically, the basic UPS system comprises a battery, a charger and an inverter, such that the battery provides the power supply needed to complement the main power supply from the power generation system, thus maintaining the security of the cited power supply.
However, in cases where the electrical power supply needed goes beyond the capacity of the battery or batteries comprised in the typical UPS systems, a further independent power generating system needs to be installed. Typically, this independent power generating system comprises a diesel generator, known as standby diesel generator, being a combination of a diesel engine with an electrical generator, often an alternator, to generate electrical energy. Therefore, in such cases, emergency power supply systems comprise both a UPS and a standby diesel generator. However, the problem of these emergency systems is that they are complex, expensive and require significant space in the power generation system arrangement. Moreover, a restart of the power generation system after the occurrence of a failure or disruption, is only permitted if the UPS system is again available, meaning that the batteries in the UPS need to be charged, leading to a cost and time consuming process.
It is known in the state of the art the use of fuel cells for providing uninterruptible power supply, providing long run times in a small space. A fuel cell converts the chemical energy from a fuel into electricity through a chemical reaction. Fuel cells are different from batteries in that they require a constant source of fuel and oxygen to run, but they can produce electricity continually for as long as these inputs are supplied. Fuel cells used for uninterrupted power supply are known in the state of the art, as per JP 2004129337 (A), JP 8236134 (A), CN 202034819 (U) or WO 01/71885 A1.
U.S. Pat. No. 6,992,401 B1 discloses an uninterruptable emergency power supply system for a telecommunication facility comprising proton exchange membrane fuel cells supplied with hydrogen as fuel which fuel is stored on site for immediate use in case of failure of a power supply from an external source and a power supply from micro gas turbines.
In U.S. 2007/057510 A1 is an uninterruptable emergency system for a tele-communication facility described with a fuel cell supplied with hydrogen via supply storage tanks in case the primary AC power source for example a micro gas turbine generator is out of service.
A combined power generation system comprising a fuel cell and a gas turbine is known from document U.S. Pat. No. 5,482,791: the fuel cell generates electric power which, together with the electric power generated by a generator driven by the gas turbine is sent to an electric power system. However, part of this power is consumed by an electric motor driving an air compressor, needed to feed the fuel cell, so the efficiency of this power generation system is reduced and further fuel cells are needed in case of large demand operating gas turbines, which is costly and which makes the system more complex.
The present invention is intended to solve the above-mentioned disadvantages and limitations in the prior art, as it will be further explained in detail.